1. Field of the Invention
The present invention relates to an image processing technique that inputs a moving image and corrects the moving image and, more particularly, to an image analysis technique and image processing technique which extract feature amounts of a moving image.
2. Description of the Related Art
Conventionally, various image correction techniques have been proposed to improve image data. Feature amounts of a moving image may include color, luminance, tone, brightness, hue and chroma of that image data. An image correction technique may, for example, extract these feature amounts from an image and apply tone correction, sharpness correction, color balance correction, white balance correction, and exposure correction to the image data based on the extracted feature amounts.
The aforementioned image correction technique can be applied to image correction of not only a still image but also a moving image. By applying the aforementioned corrections to each frame (to be referred to as a “frame image” hereinafter) that forms a moving image, the image quality can be corrected.
However, when the aforementioned image correction technique is applied to a moving image, since it executes correction processing for each frame, correction values of a current frame may often be different from those of the previous and next frames, and these correction value differences may be recognized as image quality variations. In particular, when a moving image has a small motion from one frame to the next, the image correction may be excessively applied due to errors of feature amounts, and such correction result may be recognized as deterioration. As a method of solving this problem, a method of smoothing feature amounts extracted from the current frame image and those extracted from the previous frame image, and setting the smoothed feature amounts as those of the current frame, is possible. However, with this method, when a large change occurs between frames, feature amounts cannot be changed to a large enough extent, resulting in a poor result.
As a method of solving the problem regarding this poor result, a method to correct the feature amounts of the current frame image and set the corrected feature amounts as those of both the previous and next frame images has been proposed (Japanese Patent Laid-Open No. 2005-269542). More specifically, tentative feature amounts are calculated and are adjusted according to a result of a cut point analysis unit to set them as feature amounts.
However, when feature amounts of a moving image are to be calculated, as described above, often they may be different for different (e.g. the prior and future) frames. In this case, even when the tentative feature amounts of the current frame are adjusted as in the conventional method, a substantial influence by errors are included without being wanted, and a stable image quality cannot be obtained. Moreover, with the conventional method, since a scene change of a moving image is discriminated by analyzing variations of individual images, the precision of discrimination is low. Furthermore, with the conventional method, since tentative feature amounts are calculated for all frames, a heavy load is imposed on arithmetic processing.